Stroboscopic apparatus



Sept. 17, 1935.

I w. F. WESTENDORP 2,014,957

STROBOSCOPIC APPARATUS Filed June 10, 1931 Fig.2.

Fig.5.

Inventor Wil lern F. Westenc lorp, V

b Mmm His Attorney.

Patented Sept. 17, 1935 v STRQBOSCOPIC APPARATUS Willem F. Westendorp, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 10, 1931, Serial No. 543,481 5 Claims. (01. 176-124) My invention relates to stroboscopic apparatus and particularly to stroboscopic apparatus of that type in which light flashes are produced by the periodic operation of a light source. It is 5 the object of my invention to provide an improved apparatus of the above mentioned type which is operable from a source of low voltage, which shall have high illuminating power during the short intervals of illumination and which is simple, efiicient and reliable.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

5 Referring to the drawing, Fig. 1 is a diagram illustrating one embodiment of my invention adapted for operation from a direct current source and in which the frequency of the flashes is controlled by the circuit; Figs. 2 and 3 illustrate lo modified forms in which the frequency of the flashes is controlled by a contact device; Figs. 4, 5 and 6 illustrate modifications which are adapted for operation from a source of alternating current the frequency of the current determining the flash 5 frequency.

In its more essential features the stroboscopic apparatus which I have devised comprises a positive column discharge lamp having main and auxiliary electrodes, a condenser arranged to be charged from a low voltage source and to discharge through the lamp supplying the operating current therefor and various control devices for regulating the instant at which the lamp is operated and the number of operations per second. 5 The positive column discharge lamp i comprises a suitable transparent envelope such as glass or quartz of tubular form and containing a gas or vapor, for example, argon, neon, helium, krypton, xenon, mercury, or sodium, or suitable gaseous mixtures. At one end of the envelope is the cathode 2 preferably a hot or thermionic cathode and at the opposite end the main'anode 3. For supplying the operating current to the lamp i, 5 I provide the capacitor 4 which connects through the inductance 5 with the main anode 3 and with the cathode 2 whereby, the discharge of the capacitor supplies current to cause a flash operation of the lamp. The capacitor whose value 50 may for example be from 1 mi. to 100 mi. depending upon the amount of light desired from the lamp is charged by being connected through the variable resistor B with the source I of direct current of low voltage. Throughout the specifica- 55 tion and claims in this case it is to be understood that by low voltage I refer to voltages of the order of 110 or 220 volts.

Because of'the length of the lamp l a voltage of the order of 2000 volts might be required to start the discharge between the cathode and the main anode} To reduce the voltage required for the starting of the lamp to that which may be obtained from the low voltage source 1, I provide the lamp I with one or more auxiliary anodes 8, 9, l0 and II and I connect these auxiliary l0 anodes through suitable resistances I2 with the same side of the source I as that to which the main anode 3 is connected. Resistances I2, for example, may have a value of 2000 ohms for each of the anodes 8 and 9, 1000 ohms for anode l0, l5 and 500 ohms for anode I I. Because of the high resistances between the auxiliary anodes and the source of current the discharge in the tube between the auxiliary anodes and the cathode is not sufiicient to produce a; luminous efiect. ever, the tube is maintained in an ionized condition for a suificient part of its full length so that as soon as the capacitor 4 reaches a predetermined condition of charge, the voltage applied to the main anode is sufiicient to start the tube into luminous operation. Thus, for example, by the use of the auxiliary anodes a voltage of approximately 70 volts only need be applied between the cathode and main anode to produce the 'full operation of the lamp. The positive column discharge lamp which I have illustrated on the drawing and described above is described and claimed in U. S. Letters Patent No. 1,958,239 to Found and Westendorp dated May 8, 1934:. v

In the operation of-that form of my invention shown by Fig. l, the capacitor 3 alternately receives a charge from the direct current source I through the variable resistor 6 and discharges through the inductance 5 and the lamp 8. The duration of the dash is determined by the induc- 49 tance and the capacitance of the discharge circuit, the discharge current being approximately a hal sine wave. Although on the drawing I have shown the inductance element 5, I have found that in certain cases I may obtain sufiicient in 5 ductance from the circuituoop by which the capacitor t is connected to the main electrodes of the lamp. The frequency of operation of the lamp may be controlled within certain limits by the adjustment of the variable resistor 6. In dis- 50 a charging through the lamp, the capacitor 3 will discharge to a negative potential on account of the constant resistance of the lamp and the inductive reactance of inductance '5 in the discharge circuit whereby it will be seen that a How- 20 g greater quantity of electricity is drawn from the I capacitor, resulting in a somewhat longer period of illumination f the lamp. 1 The illumination petacts is shown the battery l1 and the primary of.

the transformer IO whose secondary connects with the negative side of the source of supply and with auxiliary anode I! through the resistance 20. The other auxiliary anodes Ii, 22 and 23 connect through suitable resistances 24 with the positive side of the source of supply which resistances may have the same values as the corresponding resistances of Fig. 1. The main anode in this case connects with the positive side of the source through the fixed resistor 28. It is to be noted that the energy which the transformer needs to deliver to the auxiliary anode II is very small and ,that the movable contact I! may be 25 mounted, for example, directly on the shaft of a machine being studied in which case synchrofinism is automatically secured. By shifting the contact l5 around the shaft in sucha case it is very easy to cause the flash to come at any instantof the rotation. As in the form shown by J Fig. 1, auxiliary anodes 2|, :2 and}! serve to ionize the tube in the region thereof but due to the resistances 24 in circuit therewith the illumi nation from the discharge is negligijile As soon as auxiliary anode l9, however, is made operative by the impulse from transformer I! at the sep- ,aration of contacts I! and ii the ionization is carried on up to the main anode and the lamp becomesluminous.

in certain respects to that shown by Fig. 2. In this figure the rotatable contact is connected 'dl-.

rectly with the lower three auxiliary anodes I! while the upper two auxiliary anodes 2! connect with the main anode 3. To reduce sparking at the contacts I have shown the capacitor 28. and

\ resistor 29 in circuit therewith. It will be noted that in this form of my invention the starting of, the lamp is determined by the closing of a circuit rather than thebreaking of a current. Hence the instant of starting will always be in the same phase positionand not dependent upon the formation of a spark. In this case, as soon as aw:-

iliary anodes 26 are energized by the closing of the circuit at contacts 15 and II, the ionization is carried up to auxiliary anodes 21. I

The modification illustrated by Fig. 4 is for operation from .an alternating current source,

. which for example, may be 110 V. cycles. In

60 this form of my invention, I have shown the lamp i having a single'auxiliary anode II which cone nects through resistor 3! with the secondary'of the transformer", the primary of this transformer being connected across the source of altemating current supply, II. I have shown the a circuit by which the capacitor 4 is chargedfrom Qthe'supply Sfas includingtthe' rectifier I4 and the "inductance 35. If desired the rectifier I4 and the inductance 38 may be omitted and a resistiliary-anodeis-supplied is constructed to'si'ep up that-voltage crane supply circuit. Close to the peakof the voltage w ve applied to the auxiliary The modification shown by Fig. 3 is similar nce' substituted therefor; however, in that case undesirable lossof heat may occur in the 're- I'he transformer 82 by which the auxanode a discharge between the cathode and this anode will start and will draw a very small current. This current, however, will cause the main discharge to occur between the cathode and the main anode 3,such a discharge being supplied 5 from the capacitor I. This operation occurs once every cycle as the lamp conducts only in one direction. If desired, the transformer 32 may be of some well known special design to produce a peaked secondary voltage wave which may be 10 found more satisfactory for determining the c!- act instant of the starting of the lamp. v

In the modified form shown by Fig. 5, I employ no higher voltage than that of the source of alternating current supply 33 which, for example, 10 may be 110 V. In this case all four of the auxiliary electrodes 31 connect through suitable resistances II with one side of the supply circuit, In this case, however, the first of the auxiliary anodes I1 is retarded a slight amount by con- 20 necting the capacitor 39 between it and the cathode. As a result of this'arrangem ent the starting of the lamp is less dependent upon the wave shape of the voltage source.

In the modification comprising Pig. 6, I have 25 shown an arrangement for accomplishing a similar result. In this case the first auxiliary elec-- trode 40' is energized by being connected to the secondary of transformer 4 iwhich is constructed to give a peaked secondary voltage wave. The 30 transformer 41 thus puts a voltage peak on the auxiliary electrode 4| in a definite part of the cycle and thus starts the operation of the lamp always in the same phase position. If desired, the secondary of the transformer ll may also be 35 connected to one or more of the other auxiliary anodes l1. 1

While I have not described the auxiliary anodes of the various modifications as having any par- I ticular form or shape, it will be erstood that 0 at least the first auxiliary anode, or one nearest to the cathode, preferably is in the form of a ring arranged at right angles toethe axis of the tube, such a construction being shown and it will be apparent that various other modifica- 'tionsmaybemadewithoutdepartingfromthe spirit and scope of my invention which modifi-- cations Iaimto cover by the appendedclaims. What! claim asnewanddesiretosecureby Letters Patent of the United States is: 00

- -1. A stroboscopic apparatus comprising a low voltage positive column lamp having a thermionic cathode, a main anode and an auxiliary anode,

' a capacitor having a discharge circuit connected with said cathode and main anode for supplying the operating current to the hinp, means including a resistor for connecting the capacitor with a source of low voltage alternating current and a transformer excited from said source having its secondary connected with said auxiliary anode. Y V

2. A stroboscopic apparatus comprising a low voltage positive-column lamp having a thermionic cathode, a main anode and an auxiliary anode,

" a capacitor connected to be charged from a source of low voltage and having connections with the cathode and main anode for supplying the operating current to the lamp and a device operable intermittently to connect the auxiliary anode with saidlow voltage source.

3. A stroboscopic apparatus comprising a low voltage positive column lamp having a thermionic cathode, a main anode and a series of auxiliary anodes arranged therebetween, a source of low tive column discharge lamp having a main anode and a thermionic cathode arranged at opposite ends thereof, a capacitor connected with said anode and cathode for supplyingthe operating current to the lamp, a plurality of starting anodes in said lamp arranged in spaced relation between said cathode and main anodeand means for supplying a voltage to said capacitor for charging the same and to said cathode and starting anodes, said voltage being insufllcient to initiate a discharge in said lamp between the cathode and main anode. 1

5. A stroboscopic apparatus comprising a positive column discharge lamp having a main anode and a thermionic cathode arranged at opposite ends thereof and having an intermediate starting anode, a capacitor connected with said main.

anode and cathode for supplying the operating current to the lamp, a source of voltage insufll-t 

